Ophthalmic Injection System

ABSTRACT

An ophthalmic injection system has a tip segment attachable to and removable from a limited reuse assembly. The tip segment has a dispensing chamber housing, a plunger, a needle, a temperature control device, a thermal sensor, and a first housing at least partially enclosing the dispensing chamber housing, the temperature control device and the plunger. The limited reuse assembly has an actuator with a shaft, a power source for providing power to the actuator, a controller for controlling the actuator, a mechanical linkage interface, and a second housing at least partially enclosing the power source, the controller, and the actuator. The mechanical linkage interface is coupled to the actuator shaft and has a mating surface on one end. The substance is injected after the temperature of the substance is altered.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/581,629 filed Oct. 16, 2006, U.S. patent application Ser.No. 11/581,630 filed Oct. 16, 2006, U.S. patent application Ser. No.11/581,591 filed Oct. 16, 2006, and U.S. patent application Ser. No.11/435,906 filed May 17, 2006.

BACKGROUND OF THE INVENTION

The present invention relates to a single-use medical device and moreparticularly to a two-piece ophthalmic drug delivery device with adisposable tip end containing an improved plunger linkage and seal.

Several diseases and conditions of the posterior segment of the eyethreaten vision. Age related macular degeneration (ARMD), choroidalneovascularization (CNV), retinopathies (e.g., diabetic retinopathy,vitreoretinopathy), retinitis (e.g., cytomegalovirus (CMV) retinitis),uveitis, macular edema, glaucoma, and neuropathies are several examples.

These, and other diseases, can be treated by injecting a drug into theeye. Such injections are typically manually made using a conventionalsyringe and needle. FIG. 1 is a perspective view of a prior art syringeused to inject drugs into the eye. In FIG. 1, the syringe includes aneedle 105, a luer hub 110, a chamber 115, a plunger 120, a plungershaft 125, and a thumb rest 130. As is commonly known, the drug to beinjected is located in chamber 115. Pushing on the thumb rest 130 causesthe plunger 120 to expel the drug through needle 105.

In using such a syringe, the surgeon is required to puncture the eyetissue with the needle, hold the syringe steady, and actuate the syringeplunger (with or without the help of a nurse) to inject the fluid intothe eye. The volume injected is typically not controlled in an accuratemanner because the vernier on the syringe is not precise relative to thesmall injection volume. Fluid flow rates are uncontrolled. Reading thevernier is also subject to parallax error. Tissue damage may occur dueto an “unsteady” injection. Reflux of the drug may also occur when theneedle is removed from the eye.

An effort has been made to control the delivery of small amounts ofliquids. A commercially available fluid dispenser is the ULTRA™ positivedisplacement dispenser available from EFD Inc. of Providence, R.I. TheULTRA dispenser is typically used in the dispensing of small volumes ofindustrial adhesives. It utilizes a conventional syringe and a customdispensing tip. The syringe plunger is actuated using an electricalstepper motor and an actuating fluid. Parker Hannifin Corporation ofCleveland, Ohio distributes a small volume liquid dispenser for drugdiscovery applications made by Aurora Instruments LLC of San Diego,Calif. The Parker/Aurora dispenser utilizes a piezo-electric dispensingmechanism. Ypsomed, Inc. of Switzerland produces a line of injectionpens and automated injectors primarily for the self-injection of insulinor hormones by a patient. This product line includes simple disposablepens and electronically-controlled motorized injectors.

U.S. Pat. No. 6,290,690 discloses an ophthalmic system for injecting aviscous fluid (e.g. silicone oil) into the eye while simultaneouslyaspirating a second viscous fluid (e.g. perflourocarbon liquid) from theeye in a fluid/fluid exchange during surgery to repair a retinaldetachment or tear. The system includes a conventional syringe with aplunger. One end of the syringe is fluidly coupled to a source ofpneumatic pressure that provides a constant pneumatic pressure toactuate the plunger. The other end of the syringe is fluidly coupled toan infusion cannula via tubing to deliver the viscous fluid to beinjected.

It would be desirable to have a portable hand piece for injecting a druginto the eye that includes a relatively inexpensive tip segment that canbe attached to and removed from a reusable assembly. Placing the moreexpensive components, including electronics and a drive mechanism, inthe reusable assembly, while keeping the sterile components in the tipassembly, improves the efficiency and cost-effectiveness of a drugdelivery system. It would be desirable to have a reusable assembly thatcontains the functionally and components for the injection process. Itwould also be desirable to have a disposable tip segment that can beeasily attached to the reusable assembly for the injection, and theneasily removed and discarded after the injection. Such a system providesnumerous benefits over prior art injectors.

SUMMARY OF THE INVENTION

In one embodiment consistent with the principles of the presentinvention, the present invention is an ophthalmic injection system. Theophthalmic injection system has a tip segment attachable to andremovable from a limited reuse assembly. The tip segment has adispensing chamber housing, a plunger, a needle, a temperature controldevice, a thermal sensor, and a first housing at least partiallyenclosing the dispensing chamber housing, the temperature control deviceand the plunger. The dispensing chamber housing has an inner surface andan outer surface. The inner surface partially defines a dispensingchamber for receiving a quantity of a substance. The plunger is engagedwith the inner surface of the dispensing chamber housing. is capable ofsliding in the dispensing chamber housing, and is fluidly sealed to theinner surface of the dispensing chamber housing. The plunger has aplunger interface. The needle is fluidly coupled to the dispensingchamber. The temperature control device at least partially surrounds thedispensing chamber housing and alters a temperature of the substance inthe dispensing chamber. The thermal sensor is located near thedispensing chamber housing and measures a temperature near thedispensing chamber housing. The limited reuse assembly has an actuatorwith a shaft, a power source for providing power to the actuator, acontroller for controlling the actuator, a mechanical linkage interface,and a second housing at least partially enclosing the power source, thecontroller, and the actuator. The mechanical linkage interface iscoupled to the actuator shaft and has a mating surface on one end. Thesubstance is injected after the temperature of the substance is altered.

In another embodiment consistent with the principles of the presentinvention, the present invention is an ophthalmic injection system. Theophthalmic injection system has a tip segment attachable to andremovable from a limited reuse assembly. The tip segment has adispensing chamber housing, a plunger, a needle, a temperature controldevice, a thermal sensor, a pair of tip interface connectors, and afirst housing at least partially enclosing the dispensing chamberhousing, the temperature control device and the plunger. The dispensingchamber housing has an inner surface and an outer surface. The innersurface partially defines a dispensing chamber for holding a quantity ofa substance. The plunger is engaged with the inner surface of thedispensing chamber housing, is capable of sliding in the dispensingchamber housing, and is fluidly sealed to the inner surface of thedispensing chamber housing. The plunger has a plunger interface. Theneedle is fluidly coupled to the dispensing chamber. The temperaturecontrol device at least partially surrounds the dispensing chamberhousing and alters a temperature of the substance in the dispensingchamber. The thermal sensor is located near the dispensing chamberhousing and measures a temperature near the dispensing chamber housing.The pair of tip interface connectors are located on an interfacingsurface of the tip segment. The limited reuse assembly has an actuatorwith a shaft, a power source for providing power to the actuator, acontroller for controlling the actuator, a mechanical linkage interface,a pair of limited reuse assembly interface connectors, and a secondhousing at least partially enclosing the power source, the controller,and the actuator. The mechanical linkage interface is coupled to theactuator shaft and has a mating surface on one end. The pair of limitedreuse assembly interface connectors are located on an interfacingsurface of the limited reuse assembly. The substance is injected afterthe temperature of the substance is altered.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are intended to provide further explanation of the invention asclaimed. The following description, as well as the practice of theinvention, set forth and suggest additional advantages and purposes ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a perspective view of a prior art syringe.

FIG. 2 is one view of an ophthalmic medical device including adisposable tip segment and a limited reuse assembly according to anembodiment of the present invention.

FIG. 3 is another embodiment of a limited reuse assembly according tothe principles of the present invention.

FIG. 4 is a cross section view of another embodiment of a limited reuseassembly according to the principles of the present invention.

FIG. 5 is a cross section view of a disposable tip segment and a limitedreuse assembly according to an embodiment of the present invention.

FIG. 6 is a cross section view of a disposable tip segment for anophthalmic medical device according to an embodiment of the presentinvention.

FIG. 7 is a cross section view of a disposable tip segment for anophthalmic medical device according to an embodiment of the presentinvention.

FIG. 8 is a cross section view of a disposable tip segment and a partialview of a limited reuse assembly according to an embodiment of thepresent invention.

FIG. 9A is a cross section view of a disposable tip segment for anophthalmic medical device according to an embodiment of the presentinvention.

FIG. 9B is an end view of the embodiment of FIG. 9A.

FIGS. 10A-10D are schematic depictions of four different circuits thatmay be included in embodiments of the present invention.

FIG. 11 is end view of a limited reuse assembly according to theprinciples of the present invention.

FIG. 12 is a cross section view of a limited reuse assembly according toan embodiment of the present invention.

FIG. 13 is a cross section view of a limited reuse assembly according toan embodiment of the present invention.

FIGS. 14 and 15 are cross section views of two subassemblies accordingto the principles of the present invention.

FIG. 16 is a cross section view of a limited reuse assembly, tipsegment, and a charging base according to the principles of the presentinvention.

FIGS. 17A and 17B are flow charts of one method of injecting a substanceinto an eye according to the principles of the present invention.

FIG. 18 is a flow chart of one method relating to injecting a substanceinto an eye according to the principles of the present invention.

FIG. 19 is a flow chart of one method relating to injecting a substanceinto an eye according to the principles of the present invention.

FIG. 20 is a flow chart of one method relating to injecting a substanceinto an eye according to the principles of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made in detail to the exemplary embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers are usedthroughout the drawings to refer to the same or like parts.

FIG. 2 is one view of an ophthalmic medical device including adisposable tip segment and a limited reuse assembly according to anembodiment of the present invention. In FIG. 2, the medical deviceincludes a tip segment 205 and a limited reuse assembly 250. The tipsegment 205 includes a needle 210, a housing 215, and an optional light275. The limited reuse assembly 250 includes a housing 255, a switch270, a lock mechanism 265, and a threaded portion 260.

Tip segment 205 is capable of being connected to and removed fromlimited reuse assembly 250. In this embodiment, tip segment 205 has athreaded portion on an interior surface of housing 215 that screws ontothe threaded portion 260 of limited reuse assembly 250. In addition,lock mechanism 265 secures tip segment 215 to limited reuse assembly250. Lock mechanism 265 may be in the form of a button, a slidingswitch, or a cantilevered mechanism. Other mechanisms for connecting tipsegment 205 to limited reuse assembly 250, such as those involvingstructural features that mate with each other, are commonly known in theart and are within the scope of the present invention.

Needle 210 is adapted to deliver a substance, such as a drug, into aneye. Needle 210 may be of any commonly known configuration. Preferably,needle 210 is designed such that its thermal characteristics areconducive to the particular drug delivery application. For example, whena heated drug is to be delivered, needle 210 may be relatively short(several millimeters) in length (for thermal purposes) to facilitateproper delivery of the drug.

Switch 270 is adapted to provide an input to the system. For example,switch 270 may be used to activate the system or to turn on atemperature control device. Other switches, buttons, or user-directedcontrol inputs are commonly known and may be employed with limited reuseassembly 250 and/or tip segment 205.

Optional light 275 is illuminated when tip segment 205 is ready to beused. Optional light 275 may protrude from housing 215, or it may becontained within housing 215, in which case, optional light 275 may beseen through a clear portion of housing 215. In other embodiments,optional light 275 may be replaced by an indicator, such as a liquidcrystal display, segmented display, or other device that indicates astatus or condition of disposable tip segment 205. For example, optionallight 275 may pulse on and off to indicate other states, such as, butnot limited to a system error, fully charged battery, insufficientlycharged battery or faulty connection between the tip segment 205 andlimited use assembly 250. While shown on tip segment 205, optional light275 or an additional indicator may be located on limited reuse assembly250.

FIG. 3 is another embodiment of a limited reuse assembly according tothe principles of the present invention. Limited reuse assembly 250includes a button 308, a display 320, and a housing 330. Disposable tipsegment 205 attaches to end 340 of limited reuse assembly 250. Button308 is actuated to provide an input to the system. As with switch 270,button 308 may activate a temperature control device or initiateactuation of a plunger. Display 320 is a liquid crystal display,segmented display, or other device that indicates a status or conditionof disposable tip segment 205 or limited reuse assembly 250.

FIG. 4 is a cross section view of another embodiment of a limited reuseassembly according to the principles of the present invention. In FIG.4, power source 505, interface 517, actuator 515, and actuator shaft 510are located in housing 255. The top part of housing 255 has a threadedportion 260. Lock mechanism 265, switch 270, button 308, and indicators306, 307 are all located on housing 255.

Power source 505 is typically a rechargeable battery, such as a lithiumion battery, although other types of batteries may be employed. Inaddition, any other type of power cell is appropriate for power source505. Power source 505 provides power to the system, and moreparticularly to actuator 515. Power source 505 also provides power to atip segment connected to limited reuse assembly 250. In such a case,power source 505 may provide power to a temperature control device (notshown) located in the tip segment. Optionally, power source 505 can beremoved from housing 255 through a door or other similar feature (notshown).

Interface 517 is typically an electrical conductor that allows power toflow from power source 505 to actuator 515. Other interfaces, likeinterface 517, may also be present to provide power to other parts ofthe system.

Actuator shaft 510 is connected to and driven by actuator 515. Actuator515 is typically a stepper motor or other type of motor that is capableof moving actuator shaft 510 precise distances. In one embodiment,actuator shaft 510 is connected via a mechanical linkage to a tipsegment that delivers a drug into an eye. In such a case, actuator 515is a stepper motor that can precisely move shaft 510 to deliver aprecise quantity of drug into the eye. Actuator 515 is secured to aninterior surface of housing 255 by, for example, tabs that engage theouter surface of actuator 515.

In other embodiments, actuator 515 is a linear actuator or lineardriver. In such a case, actuator 515 may be a spring or spring drivenmechanism, a geared DC motor with a rotary sensor coupled to a lineardrive or a dc motor coupled to a linear drive with a linear sensor, or alinear stepper motor. Other types of motors, like a rotational permanentmagnet motor, may also be used for actuator 515.

Lock mechanism 265, switch 270, and button 308 are all located onhousing 255 so that they can be manipulated by hand. Likewise,indicators 306, 307 are located on housing 255 so that they can beviewed. Lock mechanism 265, switch 270, button 308, and indicators 306,307 are also connected to a controller (not shown) via interfaces (notshown) located in housing 255.

FIG. 5 is a cross section view of a disposable tip segment and a limitedreuse assembly according to an embodiment of the present invention. FIG.5 shows how tip segment 205 interfaces with limited reuse assembly 250.In the embodiment of FIG. 5, tip segment 205 includes assembly 555,plunger interface 420, plunger 415, dispensing chamber housing 425, tipsegment housing 215, temperature control device 450, thermal sensor 460,needle 210, dispensing chamber 405, interface 530, and tip interfaceconnector 453. Limited reuse assembly 250 includes mechanical linkageinterface 545, actuator shaft 510, actuator 515, power source 505,controller 305, limited reuse assembly housing 255, interface 535, andlimited reuse assembly interface connector 553.

In tip segment 205, plunger interface 420 is located on one end ofplunger 415. The other end of plunger 415 forms one end of dispensingchamber 405. Plunger 415 is adapted to slide within dispensing chamber405. The outer surface of plunger 415 is fluidly sealed to the innersurface of dispensing chamber housing 425. Dispensing chamber housing425 surrounds the dispensing chamber 405. Typically, dispensing chamberhousing 425 has a cylindrical shape. As such, dispensing chamber 405also has a cylindrical shape. In tip segment 205, assembly 555 includesany number of components as described below.

Needle 210 is fluidly coupled to dispensing chamber 405. In such a case,a substance contained in dispensing chamber 405 can pass through needle210 and into an eye. Temperature control device 450 at least partiallysurrounds dispensing chamber housing 425. In this case, temperaturecontrol device 450 is adapted to heat and/or cool dispensing chamberhousing 425 and any substance contained in dispensing chamber 405.Interface 530 connects temperature control device 450 with tip interfaceconnector 453.

The components of tip segment 205, including dispensing chamber housing425, temperature control device 450, and plunger 415 are at leastpartially enclosed by tip segment housing 215. In one embodimentconsistent with the principles of the present invention, plunger 415 issealed to the interior surface of dispensing chamber housing 425. Thisseal prevents contamination of any substance contained in dispensingchamber 405. For medical purposes, such a seal is desirable. This sealcan be located at any point on plunger 415 or dispensing chamber housing425.

In limited reuse assembly 250, power source 505 provides power toactuator 515. An interface (not shown) between power source 505 andactuator 515 serves as a conduit for providing power to actuator 515.Actuator 515 is connected to actuator shaft 510. When actuator 515 is astepper motor, actuator shaft 510 is integral with actuator 515.Mechanical linkage interface 545 is connected to actuator shaft 510. Inthis configuration, as actuator 515 moves actuator shaft 510 upwardtoward needle 210, mechanical linkage interface 545 also moves upwardtoward needle 210. In other embodiments of the present invention,mechanical linkage interface 545 and actuator shaft 510 are a singlecomponent. In other words, a shaft connected to actuator 515 includesboth actuator shaft 510 and mechanical linkage interface 545 as a singleassembly.

Controller 305 is connected via interface 535 to limited reuse assemblyinterface connecter 553. Limited reuse assembly interface connecter 553is located on a top surface of limited reuse assembly housing 255adjacent to mechanical linkage interface 545. In this manner, bothlimited reuse assembly interface connector 553 and mechanical linkageinterface 545 are adapted to be connected with tip interface connector453 and plunger interface 420, respectively.

Controller 305 and actuator 515 are connected by an interface (notshown). This interface (not shown) allows controller 305 to control theoperation of actuator 515. In addition, an interface (not shown) betweenpower source 505 and controller 305 allows controller 305 to controloperation of power source 505. In such a case, controller 305 maycontrol the charging and the discharging of power source 505 when powersource 505 is a rechargeable battery.

Controller 305 is typically an integrated circuit with power, input, andoutput pins capable of performing logic functions. In variousembodiments, controller 305 is a targeted device controller. In such acase, controller 305 performs specific control functions targeted to aspecific device or component, such as a temperature control device or apower supply. For example, a temperature control device controller hasthe basic functionality to control a temperature control device. Inother embodiments, controller 305 is a microprocessor. In such a case,controller 305 is programmable so that it can function to control morethan one component of the device. In other cases, controller 305 is nota programmable microprocessor, but instead is a special purposecontroller configured to control different components that performdifferent functions. While depicted as one component in FIG. 5,controller 305 may be made of many different components or integratedcircuits.

Tip segment 205 is adapted to mate with or attach to limited reuseassembly 250. In the embodiment of FIG. 5, plunger interface 420 locatedon a bottom surface of plunger 415 is adapted to mate with mechanicallinkage interface 545 located near a top surface of limited reuseassembly housing 255. In addition, tip interface connector 453 isadapted to connect with limited reuse assembly interface connector 553.When tip segment 205 is connected to limited reuse assembly 250 in thismanner, actuator 515 and actuator shaft 510 are adapted to drive plunger415 upward toward needle 210. In addition, an interface is formedbetween controller 305 and temperature control device 450. A signal canpass from controller 305 to temperature control device 450 throughinterface 535, limited reuse assembly interface connector 553, tipinterface connector 453, and interface 530.

In operation, when tip segment 205 is connected to limited reuseassembly 250, controller 305 controls the operation of actuator 515.When actuator 515 is actuated, actuator shaft 510 is moved upward towardneedle 210. In turn, mechanical linkage interface 545, which is matedwith plunger interface 420, moves plunger 415 upward toward needle 210.A substance located in dispensing chamber 405 is then expelled throughneedle 210.

In addition, controller 305 controls the operation of temperaturecontrol device 450. Temperature control device 450 is adapted to heatand/or cool dispensing chamber housing 425 and its contents. Sincedispensing chamber housing 425 is at least partially thermallyconductive, heating or cooling dispensing chamber housing 425 heats orcools a substance located in dispensing chamber 405. Temperatureinformation can be transferred from thermal sensor 460 through interface530, tip interface connector 453, limited reuse assembly interfaceconnector 553, and interface 535 back to controller 305. Thistemperature information can be used to control the operation oftemperature control device 450. When temperature control device 450 is aheater, controller 305 controls the amount of current that is sent totemperature control device 450. The more current sent to temperaturecontrol device 450, the hotter it gets. In such a manner, controller 305can use a feed back loop utilizing information from thermal sensor 460to control the operation of temperature control device 450. Any suitabletype of control algorithm, such as a proportional integral derivative(PID) algorithm, can be used to control the operation of temperaturecontrol device 450.

FIG. 6 is a cross section view of a disposable tip segment for anophthalmic medical device according to an embodiment of the presentinvention. In FIG. 6, disposable tip segment 205 includes housing 215,needle 210, plunger 415, plunger interface 420, dispensing chamber 405,dispensing chamber housing 425, assembly 555, temperature control device450, thermal sensor 460, optional luer 430, tip interface connectors451, 452, and 453, and interfaces 461, 462, and 463. Disposable tipsegment 205 operates as a disposable injection device.

In the embodiment of FIG. 6, plunger 415 is located in dispensingchamber housing 425. Dispensing chamber 405 is enclosed by dispensingchamber housing 425 and plunger 415. Plunger 415 forms a fluid seal withthe interior surface of dispensing chamber housing 425. Needle 210 isfluidly coupled to dispensing chamber 405. In this manner, a substancelocated in dispensing chamber 405 can be contacted by plunger 415 andpushed out of needle 210. Needle 210 may be secured to disposable tipsegment 205 by an optional luer 430 or may be permanently attached.Temperature control device 450 is located on dispensing chamber housing425 and at least partially surrounds dispensing chamber 405. Housing 215forms an outer skin on disposable tip segment 205.

In various embodiments of the present invention, temperature controldevice 450 is a heating and/or a cooling device. Temperature controldevice 450 is in thermal contact with dispensing chamber housing 425. Assuch, temperature control device 450 is capable of changing thetemperature of the substance in dispensing chamber 405.

In FIG. 6, plunger 415 includes an o-ring. The o-ring seals against aninterior surface of dispensing chamber housing 425. In this manner, asterile seal is maintained thus preventing contamination of thesubstance in dispensing chamber 405. Plunger 415 may be made of anysuitable material, such as, for example, glass, stainless steel, or apolymer. The o-ring is typically made of rubber or a polymer. Othertypes of seals may also be used. For example, plunger 415 may contain anannular ring that is located around a periphery of plunger 415 so thatthe annular ring contacts the interior surface of dispensing chamber425. This annular ring can seal the plunger against the interior surfaceof dispensing chamber 425. In such a case, the annular ring may beintegral with plunger 415, and plunger 415 may be made of rubber or apolymer. Plunger interface 420 may be of any suitable shape. Forexample, plunger interface may be substantially bowl shaped as shown, orit may be substantially flat, conical, or spherical. It may also includea lip or other similar feature.

Tip interface connectors 451, 452, and 453 serve to provide a connectionbetween tip segment 205 and a limited reuse assembly. Interface 461connects thermal sensor 460 to tip interface connector 451. Interface462 connects temperature control device 450 to tip interface connector452. Interface 463 connects assembly 555 to tip interface connector 453.

Assembly 555 can include any of a number of different components. In oneembodiment, assembly 555 contains a fuse that is blown when the heatbutton is activated or after disposable tip segment 205 is used. In thismanner, the fuse prevents reuse of disposable tip segment 205. Inanother embodiment, assembly 555 includes a memory device that storesinformation about the type of disposable tip segment 205, dosageinformation, temperature information, plunger movement information, orany other type of information that identifies a characteristic ofdisposable tip segment 205 or a manner in which disposable tip segment205 is operated. In other embodiments, assembly 205 includes ahard-wired memory device, like a NAND flash IC, an RFID tag, ahard-wired wired circuit that can store a representation of data, like aseries of fuses and resistors connected in parallel or other type ofdevice.

A substance to be delivered into an eye, typically a drug, is located indispensing chamber 405. In this manner, the drug is contacted by theinner surface of dispensing chamber housing 425 and one face of plunger415. Temperature control device 450 is in thermal contact withdispensing chamber housing 425. In this manner, temperature controldevice 450 is adapted to control the temperature of the contents ofdispensing chamber 405.

In various embodiments of the present invention, temperature controldevice 450 heats a phase transition compound that is located indispensing chamber 405. This phase transition compound carries a drugthat is to be injected into the eye. A phase transition compound is in asolid or semi-solid state at lower temperatures and in a more liquidstate at higher temperatures. Such a substance can be heated bytemperature control device 450 to a more liquid state and injected intothe eye where it forms a bolus that erodes over time. Likewise, areverse gelation compound may be used. A reverse gelation compound is ina solid or semi-solid state at higher temperatures and in a more liquidstate at lower temperatures. Such a compound can be cooled bytemperature control device 450 to a more liquid state and injected intothe eye where it forms a bolus that erodes over time. As such,temperature control device 450 may be a device that heats a substance indispensing chamber 405 or a device that cools a substance in dispensingchamber 405 (or a combination of both). After being delivered into theeye, a phase transition compound or reverse gelation compound erodesover time providing a quantity of drug over an extended period of time.Using a phase transition compound or reverse gelation compound providesbetter drug dosage with fewer injections.

Thermal sensor 460 provides temperature information to assist incontrolling the operation of temperature control device 450. Thermalsensor 460 may be located near dispensing chamber housing 425 andmeasures a temperature near dispensing chamber housing 425. Thermalsensor 460 may also be located in thermal contact with dispensingchamber housing 425, in which case it measures a temperature ofdispensing chamber housing 425. In other embodiments, the temperaturethat thermal sensor 460 measures can be correlated to the temperature ofthe substance in dispensing chamber 405. In other words, a measurementof the temperature of dispensing chamber housing 425 can be used tocalculate the temperature of the substance located in dispensing chamber405. Since the thermal characteristics of dispensing chamber housing 425and the substance therein are known, and the temperature of temperaturecontrol device 450 is controllable, an application of temperaturecontrol device for a specified period of time results in a calculablechange in the temperature of the substance in dispensing chamber 405.Thermal sensor 460 may be any of a number of different devices that canprovide temperature information. For example, thermal sensor 460 may bea thermocouple or a resistive device whose resistance varies withtemperature.

In one embodiment of the present invention, the substance located indispensing chamber 405 is a drug that is preloaded into the dispensingchamber. In such a case, disposable tip segment 205 is appropriate as asingle use consumable product. Such a disposable product can beassembled at a factory with a dosage of a drug installed.

When a drug is preloaded into dispensing chamber 405, a set quantity ofthe drug can be preloaded. For example, 100 microliters of a drug can beloaded into dispensing chamber 405, and any quantity up to 100microliters can be dispensed. Information about the amount of drug indispensing chamber 205 and other dosage information can be stored inassembly 555. In such a case, plunger 415 can be moved a precisedistance to deliver a precise dosage of drug from dispensing chamber405, through needle 210, and into an eye. This provides for flexibilityof dosing and for ease of assembly.

FIG. 7 is a cross section view of a disposable tip segment for anophthalmic medical device according to an embodiment of the presentinvention. In FIG. 7, disposable tip segment 205 includes housing 215,needle 210, plunger 415, plunger interface 420, dispensing chamber 405,dispensing chamber housing 425, assembly 555, temperature control device450, thermal sensor 460, optional luer 430, tip interface connectors 452and 453, interfaces 462 and 463, and lock mechanism 471.

The embodiment of FIG. 7 functions like the embodiment of FIG. 6. Thevarious components of tip segment 205 of FIG. 7 have the samecharacteristics and operate in substantially the same way as likecomponents of FIG. 6. Lock mechanism 471 serves to attach tip segment205 to a limited reuse assembly. A mating mechanism, like lock mechanism265, on a limited reuse assembly, attaches to lock mechanism 471 andsecures tip segment 205 to a limited reuse assembly.

FIG. 8 is a cross section view of a disposable tip segment and a partialview of a limited reuse assembly according to an embodiment of thepresent invention. In FIG. 7, disposable tip segment 205 includeshousing 215, needle 210, plunger 415, plunger interface 420, dispensingchamber 405, dispensing chamber housing 425, RFID tag 1110, temperaturecontrol device 450, tip interface connector 452, and interface 462. Thepartial view of a limited reuse assembly depicts mechanical linkageinterface 545, actuator shaft 510, interface 535, limited reuse assemblyinterface connector 552, RFID reader 1120, and RFID interface 1130.

The embodiment of FIG. 8 functions like the embodiments of FIGS. 6 and7. The various components of the tip segment 205 of FIG. 8 have the samecharacteristics and operate in substantially the same way as the likecomponents of FIGS. 6 and 7. However, the embodiment of FIG. 8 uses anRFID system rather than a wired assembly 555 to store and transferinformation. RFID reader 1120 is located near the top of a limited reuseassembly adjacent to mechanical linkage interface 545. RFID tag islocated at the bottom of tip segment 205. RFID reader 1120 is designedto read information from RFID tag 1110. RFID interface 1130 is connectedto controller 305 (not shown).

RFID tag 1110 is configured to hold the same type of information thatassembly 555 may hold in the embodiments of FIGS. 5-7. In this manner,RFID tag 1110 is another type of memory. However, as is commonly know,RFID tag 1110 does not require a wired connection to RFID reader 1120.In this manner, a wireless connection between the tip segment 205 (RFIDtag 1110) and a limited reuse assembly (RFID reader 1120) can beestablished.

In one type of RFID system, a passive RFID system, RFID tag 1110 doesnot have a power supply. Instead, the passive RFID tag relies on theelectromagnetic field produced by RFID reader 1120 for its power. Theelectromagnetic field produced by RFID reader 1120 and emitted from theRFID reader antenna (not shown) induces a small electrical current inRFID tag 1110. This small electrical current allows RFID tag 1110 tooperate. In this passive system the RFID tag is designed to collectpower from the electromagnetic field emitted by the RFID reader 1120 andto transmit an outbound signal that is received by RFID reader 1120.

In operation the RFID reader antenna (not shown) transmits a signalproduced by RFID reader 1120. The RFID tag antenna (not shown) receivesthis signal and a small current is induced in RFID tag 1110. This smallcurrent powers RFID tag 1110. RFID tag 1110 can then transmit a signalthrough its RFID tag antenna to RFID reader antenna and RFID reader 1120itself. In this manner, RFID tag 1110 and RFID reader 1120 cancommunicate with each over a radio frequency link. RFID tag 1110transmits information, such as dosage information or tip segmentinformation, through RFID tag antenna to RFID reader 1120. Thisinformation is received by RFID reader 1120. In this manner, informationcan be transferred from the tip segment 205 to the limited reuseassembly. RFID reader 1120 can transmit information to RFID tag 1110 ina similar fashion. For example, RFID reader 1120 can transmitinformation such as dosage information over the radio frequency signalemitted by RFID reader 1120. RFID tag 1120 receives this radio frequencysignal with the information. RFID tag 1110 can then store thisinformation.

While the embodiment of FIG. 8 is described as having an RFID system,any other type of wireless system can be used to transfer informationbetween a limited reuse assembly 250 and tip segment 205. For example aBluetooth protocol maybe used to establish a communications link betweena limited reuse assembly 250 and tip segment 205. Information can thenbe transferred between a limited reuse assembly 250 and a tip segment205 over this communication link. Other embodiments used to transferinformation include an infrared protocol, 802.11, fire wire, or otherwireless protocol.

In one embodiment, RFID tag 1110 (or assembly 555) contains dosageinformation. Information about a proper drug dosage for a drug containedin dispensing chamber 405 may be contained on RFID tag 1110 (or assembly555). In such a case, controller 305 can read the dosage informationfrom RFID tag 1110 (or assembly 555) and operate actuator 515 in amanner suitable to deliver the proper dosage. For example, 100microliters may be contained within dispensing chamber 405. Informationstating that a dosage of 20 microliters is to be delivered into an eyemaybe stored on RFID tag 1110 (or assembly 555). In such a case,controller 305 reads the dosage information (that 20 microliters shouldbe delivered into the eye) from RFID tag 1110 (or assembly 555).Controller 305 can then operate actuator 515 to deliver the 20microliter dosage. Controller 305 can cause actuator 515 to moveactuator shaft 510 and mechanical linkage interface 545 a set distancerelated to a dosage of 20 microliters. In such a case, plunger 415 ismoved this set distance so that only 20 microliters of a drug isexpelled from needle 210 and into an eye.

In another embodiment consistent with the principles of the presentinvention, controller 305 may calculate a distance that plunger 415 mustbe moved to deliver the desired dosage. For example, if dosageinformation corresponding to a drug dosage of 20 microliters is readfrom RFID tag 1110 (or assembly 555) by controller 305, then controller305 may use this information to calculate a proper distance that plunger415 must be moved. Since the volume of dispensing chamber 405 as well asthe volume of a drug loaded in dispensing chamber 405 is known, adistance that plunger 415 must be moved to deliver that required dosagecan be calculated by controller 305. When dispensing chamber 405 has acylindrical shape, the volume of the dispensing chamber can becalculated by using the cross section area of the cylinder (the area ofa circle) times the height of the dispensing chamber. This simplemathematical formula can be used to calculate the total volume of thedispensing chamber 405. Since the cross section area of dispensingchamber 405 is constant for any given application, the height whichcorresponds to a distance that plunger 415 travels can be calculated forany dosage amount.

For example, assume that 100 microliters of a drug is loaded intodispensing chamber 405 and that the cross sectional area of dispensingchamber 405 is ten. When dispensing chamber 405 is in the shape of acylinder, the height of that cylinder is also 10. To deliver a dosage of20 microliters which corresponds to 20% of the total volume ofdispensing chamber 405, it is necessary to move plunger 415 upwardtoward needle 210 a distance of two. In other words, a dosage of 20microliters corresponds to 20% of the total volume of dispensing chamber405. In such a case, plunger 415 should be moved upward toward needle210 a distance equal to 20% of the total height of dispensing chamber405. Controller 305 can then control actuator 515 such that actuatorshaft 510 drives plunger 415 upwards a distance of 20% of the totalheight of dispensing chamber 405.

In addition, controller 305 may read information about a rate at whichplunger 415 should be moved in order to properly deliver a dosage ofdrug. In such a case, controller 305 reads information about the rate ofdrug delivery from RFID tag 1110 (or assembly 555) and uses thatinformation to operate actuator 515 to drive plunger 415 at that rate.The rate at which plunger 415 moves may be fixed or variable. In someapplications, it may be desirable to move plunger 415 faster than inother applications. For example, when the drug contained in dispensingchamber 405 is a drug that should be heated before being injected intoan eye, it maybe desirable to drive plunger 415 at a rate such that theheated drug does not cool and clog needle 210. In other applications, itmaybe desirable to move plunger 415 slowly in order to improve thedelivery of a drug contained in dispensing chamber 405.

RFID tag 1110 (or assembly 555) may also include any other type ofinformation related to the delivery of a drug. For example, RFID tag1110 (or assembly 555) may include information about the type of drugcontained in dispensing chamber 405, various characteristics of thatdrug, or other characteristics of a proper dosage or a proper deliveryof that drug. In addition, RFID tag 1110 (or assembly 555) may containsafety information, information about the proper operation of tipsegment 205, or any other information related to the tip segment orlimited reuse assembly.

In another embodiment consistent with the principles of the presentinvention, a dosage may be selectable by the medical professional who isadministering the drug. In such a case, an input device (not shown)located on limited reuse assembly 250 or on tip segment 205 may enable adoctor to select the desired drug dosage. In such a case, controller 305receives the desired drug dosage and operates actuator 515 to moveplunger 415 the required distance to deliver the desired dosage. Such auser selectable dosage scheme may be implemented simply by adding anextra input device.

It may be desirable to include dosage information on RFID tag 1110 (orassembly 555) so that a dosing error is less likely to occur. In such acase, a number of different drug delivery tip segments 205 maybemanufactured and loaded with a drug at the factory. Dosage informationcan also be loaded onto RFID tag 1110 (or assembly 555) at the factory.In such a case, a number of different tip segments each with the sameamount of drug contained in the dispensing chamber 405 but withdifferent dosage information stored on RFID tag 1110 (or assembly 555)can be manufactured and shipped. A doctor can then order the tip segment205 with the required dosage information on the RFID tag 1110 (orassembly 555). Packaging can be clearly labeled to identify the dosageinformation so that the proper dosage is administered to a patient.

FIG. 9A is a cross section view of a disposable tip segment for anophthalmic medical device according to an embodiment of the presentinvention. In FIG. 9, disposable tip segment 205 includes housing 215,needle 210, plunger 415, plunger shaft 417, plunger interface 420,dispensing chamber 405, dispensing chamber housing 425, assembly 555,temperature control device 450, thermal sensor 460, optional luer 430,tip interface connectors 452 and 453, interfaces 462 and 463, and tabs472 and 473.

The various components of tip segment 205 of FIG. 9 have the samecharacteristics and operate in substantially the same way as likecomponents of FIGS. 5-8. The embodiment of FIG. 9 includes two tabs 472and 473 that engage slots in a limited reuse assembly. After these twotabs 472 and 473 are inserted into the slots, the tip assembly 205 isrotated to lock it into place on a limited reuse assembly. The two tabs472 and 473 may be of different shapes or sizes so as to provide aproper interface between tip segment 205 and a limited reuse assembly.When these two tabs 472 and 473 are shaped or sized differently, thentip segment 405 only fits on a limited reuse assembly in oneorientation. In other embodiments of the present invention, differentshaped or sized tabs can be used with different shaped or sized slots ondifferent limited reuse assemblies. In this manner, a number ofdifferent limited reuse assemblies may be manufactured with differentshaped or sized slots to accommodate tip segments 205 with complimentaryshaped or sized tabs.

In addition, the embodiment of FIG. 9 includes a plunger shaft 417 thatis connected to plunger 415. In this embodiment, plunger 415 may beover-molded onto plunger shaft 417. Plunger shaft 417 is generallycylindrical in shape with a middle diameter that is less than a diameteron its distal and proximal ends. Plunger interface 420 is a surface onthe proximal end of plunger shaft 417. Plunger shaft 417 is typicallymade of a rigid material such as stainless steel. Plunger 415 is made ofa rubber or polymer material. In another embodiment of the presentinvention, the distal end of plunger shaft 417 has a lip over whichplunger 415 can be applied. Plunger 415 can be press-fitted onto plungershaft 417 and is retained in place by a lip on the distal end of plungershaft 417. This allows for easier assembly. Instead of over moldingplunger 415 onto a shaft, plunger 415 can be manufactured as a separatepart and pushed onto the distal end of plunger shaft 417. Plungerinterface 420 can be of any suitable shape.

FIG. 9B is an end view of the tip segment of FIG. 9A. FIG. 9B depictsthe end of tip segment 205 farthest from needle 210. This end interfaceswith a limited reuse assembly. Pictured are housing 215, plungerinterface 420, tip interface connectors 451, 452 453, 454, 455, and 456,tabs 472 and 473, and alignment slot 481.

In the embodiment of FIG. 9B, one end of plunger interface 420 is notcompletely circular. It has a flat portion that is designed to alignwith a mechanical linkage interface with a similar cross-sectionalshape. This optional feature is designed to allow proper alignment of atip segment and a limited reuse assembly. In other embodiments of thepresent invention, the cross section view of one end of plungerinterface 420 is circular.

The embodiment of FIG. 9B also includes an optional alignment slot 481to assist in properly aligning a tip segment with a limited reuseassembly. Alignment slot 481 interfaces with an alignment pin on alimited reuse assembly (581 as shown in FIG. 11). In another embodimentof the present invention, tabs 472 and 473 have different sizes.Alternatively, tabs 472 and 473 may have different shapes. The two tabs472 and 473 also assist in aligning a tip segment with a limited reuseassembly by interfacing with slots 572 and 573 of FIG. 11.

In one embodiment consistent with the principles of the presentinvention, a tip segment is placed on a limited reuse assembly such thattabs 472 and 473 are inserted into slots 572 and 573. The tip segment isthen rotated with respect to the limited reuse assembly so that tabs 472and 473 are retained in slots 572 and 573. Alignment pin 581 andalignment slot 481 are then properly aligned.

Connectors 451, 452, 453, 454, 455, and 456 electrically link a tipsegment to a limited reuse assembly. Connectors 451, 452, 453, 454, 455,and 456 interface with similar connectors 551, 552, 553, 554, 557, and556, respectively, on a limited reuse assembly (as shown in FIG. 11).These connectors provide a path for signals to pass between a tipsegment and a limited reuse assembly.

FIGS. 10A-10D are schematic depictions of four different circuits thatmay be included in embodiments of the present invention. FIG. 10A showsone of many different configurations for temperature control device 450.In FIG. 10A, temperature control device 450 is connected to connectors452 and 455. Power and/or control signals are provided to temperaturecontrol device 450 through connectors 452 and 455.

FIG. 10B shows one of many different configurations for thermal sensor460. In FIG. 10B, thermal sensor 460 is connected to connectors 451 and454. Signals are received from thermal sensor 460 through connectors 451and 454.

FIG. 10C shows one of many different configurations for a fuse 1011.Fuse 1011 may be contained within assembly 555 or may be implemented asshown in FIG. 10C. In FIG. 10C, fuse 1011 is connected betweenconnectors 453 and 456. In this embodiment, fuse 1011 acts to ensurethat the tip assembly is a single-use device. Fuse 1011 is blown whenthe heat button is activated or after disposable tip segment 205 is usedto prevent its reuse. As discussed, a controller in a limited reuseassembly detects when the connected tip segment has been used anddirects an increased current to pass through fuse 1011 thus blowing thefuse. When fuse 1011 is blown, the tip segment is no longer operable andmust be discarded.

FIG. 10D shows one of many different configurations for assembly 555. InFIG. 10D, assembly 555 is connected to connectors 453 and 456. Powerand/or control signals are provided to assembly 555 through connectors453 and 456.

Many other configurations of connectors 451, 452 453, 454, 455, and 456may be implemented. For example, while six connectors are shown, anynumber of connectors may be implemented. Further, any combination ofdifferent circuits may be contained in a tip segment.

FIG. 11 is end view of a limited reuse assembly according to theprinciples of the present invention. The end of the limited reuseassembly shown in FIG. 11 interfaces with the end of the tip assemblyshown in FIG. 9B. The end view of limited reuse assembly depicted inFIG. 11 shows housing 255, mechanical linkage interface 545, limitedreuse assembly interface connectors 551, 552, 553, 554, 557, and 556,slots 572 and 573, and alignment pin 581.

In the embodiment of FIG. 11, one end of mechanical linkage interface545 is not completely circular. It has a flat portion that is designedto align with a plunger interface with a similar cross-sectional shape.This optional feature is designed to allow proper alignment of a tipsegment and a limited reuse assembly. In other embodiments of thepresent invention, the cross section view of one end of mechanicallinkage interface 545 is circular.

The embodiment of FIG. 11 also includes an optional alignment slot 581to assist in properly aligning a tip segment with a limited reuseassembly. Alignment pin 581 interfaces with an alignment slot on a tipsegment (481 as shown in FIG. 9B). In another embodiment of the presentinvention, slots 572 and 573 have different sizes. Alternatively, slots572 and 573 may have different shapes. The two slots 572 and 573 alsoassist in aligning a tip segment with a limited reuse assembly byinterfacing with tabs 472 and 473 of the tip segment shown in FIG. 9B.

Connectors 551, 552, 553, 554, 557, and 556 electrically link a tipsegment to a limited reuse assembly. Connectors 551, 552, 553, 554, 557,and 556 interface with connectors 451, 452 453, 454, 455, and 456 on atip segment (as shown in FIG. 9B). These connectors provide a path forsignals to pass between a tip segment and a limited reuse assembly.

FIG. 12 is a cross section view of a limited reuse assembly according toan embodiment of the present invention. In FIG. 12, limited reuseassembly 250 includes mechanical linkage interface 545, actuator shaft510, actuator 515, power source 505, controller 305, limited reuseassembly housing 255, interface 535, limited reuse assembly interfaceconnector 551, displacement sensor 1215, power source controller 444,and inductive element 1225.

Displacement sensor 1215 measures the movement of actuator shaft 510.Displacement sensor may be, among other things, an optical rotaryencoder, a linear encoder, a current sensing circuit (Hall sensor), arotary potentiometer, or a linear potentiometer. In other embodiments,displacement sensor is capable of detecting if actuator 515 stalls. Forexample, a Hall sensor can detect an increased current draw by actuator515 that indicates a stall condition. Displacement sensor 1215 may alsomeasure back EMF from actuator 515. Displacement sensor 1215 may becomprised of a single component or multiple components. In oneembodiment consistent with the principles of the present invention,displacement sensor 1215 includes a device to measure the distance thatactuator shaft 510 travels and a device to detect if actuator 515stalls.

Displacement sensor 1215 measures the position of actuator shaft 510.Since mechanical linkage interface 545 is connected to actuator shaft510, displacement sensor 1215 also measures its position. Such adisplacement sensor 1215 can be used to determine if a full dosage isdelivered. If displacement sensor 1215 detects that actuator shaft 510has traveled a certain distance corresponding to a movement ofmechanical linkage interface 545 and plunger 415, then it is known thata certain dosage has been expelled from needle 210. In the case where adrug is to be delivered into an eye, displacement sensor 1215 providesinformation about the movement of actuator shaft 510 that can be used todetermine if the full dosage has been delivered.

In some cases, actuator 515 may stall, thus failing to drive actuatorshaft 510, mechanical linkage interface 545, and plunger 415 the properdistance to deliver a full dosage of a drug into an eye. In such a case,displacement sensor 1215 measures the distance that actuator shaft 510,mechanical linkage interface 545, and plunger 415 have traveled. Fromthis distance information, a delivered amount of drug can be calculated.For example, when the dispensing chamber 405 is cylindrical in shape,its circular cross-sectional area is known. The distance measured bydisplacement sensor 1215 then becomes the height of the cylinder, andthe volume of displacement can be easily calculated (by controller 305,for example). This delivered amount can be communicated, along with astall indication, via a display, such as display 320 (FIG. 3).

Displacement sensor 1215 may also provide other information useful inthe drug delivery process. For example, when a tip segment is connectedto a limited reuse assembly, actuator shaft 510 may be withdrawn orbrought to a homed position for connection of a tip segment.Displacement sensor 1215 can measure the movement of actuator shaft 510to this homed position. Actuator shaft 510 may be placed in a homedposition to allow a tip segment to be attached to a limited reuseassembly or prior to delivery of a drug. In one embodiment, informationread from displacement sensor 1215 is used to confirm that actuatorshaft 510 is in a homed position before actuator 515 is activated todeliver a drug into the eye.

The embodiment of FIG. 12 also includes power source controller 444 andinductive element 1225. These two components control the charging ofpower source 505 when power source 505 is, for example, a rechargeablebattery. Power source controller 444 includes circuitry that may performany of a number of different functions related to the charging,monitoring, and maintenance of power source 505. In other embodiments,power source controller 444 may be implemented in or integrated intocontroller 305.

In one embodiment of the present invention, power source controller 444(or controller 305, as the case may be) counts the number of times thatlimited reuse assembly 250 has been used. After the count has reached apredetermined safe number of uses, limited reuse assembly 250 isdisabled. Alternatively, power source controller 444 (or controller 305,as the case may be) counts the number of times power source 505 has beencharged (the number of charge cycles to which power source 505 has beensubjected). When the count reaches a predetermined threshold, limitedreuse assembly 250 is disabled. In other embodiments of the presentinvention power source controller 444 (or controller 305, as the casemay be) detects fault conditions or other unsafe conditions of powersource 505 and prevents further use of limited reuse assembly 250.

To charge power source 505, a current is induced in inductive element1225 when it is placed near another inductive element in a charging base(not shown). This induced current charges power source 505.

FIG. 13 is a cross section view of a limited reuse assembly according toan embodiment of the present invention. In FIG. 12, limited reuseassembly 250 includes mechanical linkage interface 545, actuator shaft510, actuator 515, power source 505, controller 305, limited reuseassembly housing 255, interface 535, limited reuse assembly interfaceconnector 551, displacement sensor 1215, power source controller 444,and charging contacts 1235.

In the embodiment of FIG. 13, contacts 1235 interface with contacts on acharging base (not shown) to provide power to power source 505. In oneembodiment, contacts 1235 are a USB-type connection such as those usedby portable electronic devices with docking stations. In one embodiment,a Molex™ CradleCon™ connector is employed. Other types of connectors mayalso be used.

FIGS. 14 and 15 are cross section views of two subassemblies accordingto the principles of the present invention. Each of these subassembliesdepicts the path from the actuator 515 to the needle 210. FIG. 14depicts a mechanical linkage interface 545 that is rigidly connected toactuator shaft 510, while FIG. 15 depicts a mechanical linkage assembly545 with a ball joint 805. The use of ball joint 805 assists in aligningmechanical linkage interface 545 with plunger interface 420.

In FIG. 14, actuator 515 has an actuator shaft 510 that is rigidlyconnected to mechanical linkage interface 545. Mechanical linkageinterface mates with plunger interface 420. Plunger 415 is disposedwithin dispensing chamber housing 425 and is sealed against an insidesurface of dispensing chamber housing 425. Dispensing chamber 405 isbounded by an interior surface of dispensing chamber housing 425 and thedistal face of plunger 415. Temperature control device 450 at leastpartially surrounds dispensing chamber housing 425. Needle 210 isfluidly coupled to dispensing chamber 405.

In FIG. 15, actuator 515 has an actuator shaft 510 that is connected toshaft 810 via a ball joint. Mechanical linkage interface 545 isrotatably connected to shaft 810 via ball joint 805. Mechanical linkageinterface mates with plunger interface 420. Plunger 415 is disposedwithin dispensing chamber housing 425 and is sealed against an insidesurface of dispensing chamber housing 425. Dispensing chamber 405 isbounded by an interior surface of dispensing chamber housing 425 and thedistal face of plunger 415. Temperature control device 450 at leastpartially surrounds dispensing chamber housing 425. Needle 210 isfluidly coupled to dispensing chamber 405.

In FIGS. 14 and 15, actuator 515 drives actuator shaft 510 upward (in adirection towards needle 210). In turn, mechanical linkage interface 545is also driven upward. When mechanical linkage interface 545 is matedwith plunger interface 420, plunger 420 is also moved upward. Asubstance contained in dispensing chamber 405 is expelled through needle210. In this manner, motion and force is transferred from actuator shaft510 to mechanical linkage interface 545 to plunger 415.

When dispensing chamber 405 contains a drug that is to be delivered intoan eye, the configurations of FIGS. 14-15 eliminate reflux when theneedle is removed from the eye. Motion of the plunger 415 is in a singledirection (a direction that expels the drug in dispensing chamber 405).When mechanical linkage interface 545 is moved in a direction away fromneedle 210, for example, after the drug has been injected into the eye,the plunger 415 remains in place. Since plunger 415 is not rigidlyconnected to mechanical linkage interface 545, plunger 415 is notretracted as mechanical linkage interface 545 is retracted.

FIG. 16 is a cross section diagram of the limited reuse assembly of FIG.13 and a charging base. In FIG. 16, a bottom surface of limited reuseassembly 250 interfaces with charging base 1615. When limited reuseassembly 250 is resting in charging base 1615, power source 505 can becharged. After being charged, limited reuse assembly 250 can be removedfrom charging base 1615. In one embodiment of the present invention,limited reuse assembly 250 with an attached tip segment 205 is placed incharging base 1615 and a substance located in dispensing chamber 405 isheated or cooled by temperature control device 450. In this manner,charging base 1615 provides the power for temperature control device450. When the substance located in dispensing chamber 405 has reachedthe proper temperature (as determined from information from thermalsensor 460), limited reuse assembly 250 with attached tip segment 205can be removed from the charging base. This saves power source 505 forthe injection process when limited reuse assembly 250 and attached tipsegment 205 are removed from charging base 1615.

FIGS. 17A and 17B are flow charts of one method of injecting a substanceinto an eye according to the principles of the present invention. In1705, a connection between a tip segment and a limited reuse assembly isrecognized. In 1710, the type of tip segment that was connected to thelimited reuse assembly is identified. For example, a drug delivery tipsegment or type of drug delivery tip segment may be identified. Suchidentification may occur by reading information from the tip segment,for example, by reading information from memory or RFID tag. In 1715,dosage information is received from the tip segment. Like theinformation relating to the type of tip segment, dosage information maybe read from a memory device in the tip segment by a controller, RFIDreader, or similar device in the limited reuse assembly.

In 1720, a temperature control device is activated to alter thetemperature of the substance that is located in the dispensing chamber.The substance may be heated or cooled as previously described. Inaddition, the heating or cooling may only take place when the tipsegment and limited reuse assembly are located on a charging base. In1725, temperature information is received from a thermal sensor that islocated near the dispensing chamber in which the substance is located.In 1730, this temperature information is used to control the temperaturecontrol device to regulate the temperature of the substance.

In 1735, the actuator shaft is moved to a homed position. For example,the actuator shaft may be completely retracted to establish a homedposition. The homed position can establish a reference point for adisplacement sensor. In other words, the displacement sensor can beginmeasuring movement of the actuator shaft from the homed position. In1740, the actuator shaft is moved until the mechanical linkage interface(which is integral with or connected to the actuator shaft) contacts theplunger interface. In this position, any further movement of theactuator shaft results in an expulsion of the substance from thedispensing chamber. When the mechanical linkage interface is in contactwith the plunger interface, the device is ready to be used to inject thesubstance into the eye. This step is taken before injecting thesubstance into the eye so that the substance can be maintained at aproper temperature for the injection. For example, the substance may beheated or cooled while the tip segment and limited reuse assembly arelocated on a charging base. When the tip segment and limited reuseassembly are removed from the charging base, the doctor may have alimited period of time to perform the injection before the temperatureof the substance falls outside of the proper temperature range. Havingthe mechanical linkage interface in contact with the plunger interfaceallows for an injection to be performed in a short amount of time.

In 1745, an input is received indicating that the substance is to bedelivered into the eye. For example the doctor may press a button thatsends a signal to the controller indicating that the actuator is to beactivated to deliver the substance. In 1750, the dosage information isused to control the operation of the actuator to deliver the properdosage at the proper rate. The substance is delivered into they eye onlyafter it is in the proper temperature range. In 1755, information isreceived from the displacement sensor. This information indicates howfar the actuator shaft has traveled. The distance the actuator shaft hastraveled correlates to a dosage. The further the shaft has traveled, themore the plunger has been displaced, and the greater the dosagedelivered. In 1760, an indication of the dosage delivered is provided.For example, a successful injection, in which the complete dosage hasbeen successfully delivered, may be indicated by a green light or by anumber (representing the amount of substance delivered in microliters).In an unsuccessful injection, the amount of substance actually deliveredis displayed. In 1765, reuse of the tip segment is prevented, forexample, by blowing a fuse in the tip segment.

FIG. 18 is a flow chart of one method relating to injecting a substanceinto an eye according to the principles of the present invention. FIG.18 depicts a method of activating the temperature control device to heator cool the substance located in the dispensing chamber while the tipsegment and limited reuse assembly are located on a charging station. In1805, a connection between a tip segment and a limited reuse assembly isrecognized. In 1810, the type of tip segment is identified. In 1815,dosage information is received from the tip segment. In 1820, it isdetermined whether or not the tip segment and limited reuse assembly arelocated on the charging base. If they are not located on the chargingbase, then in 1825, the system waits and returns to 1820. If the tipsegment and limited reuse assembly are located on the charging base,then in 1830, the temperature control device is activated to alter atemperature of the substance contained in the dispensing chamber. In1835, temperature information is received from a thermal sensor. In1840, this temperature information is used to control the temperaturecontrol device.

FIG. 19 is a flow chart of one method relating to injecting a substanceinto an eye according to the principles of the present invention. FIG.19 depicts a method relating to determining whether or not the properdosage has been delivered. In 1910, the actuator is controlled based ona dosage and dosage rate information. The actuator moves the plunger todeliver the substance. In 1920, information is received from thedisplacement sensor indicating the distance that the actuator shaft hasmoved. In 1930, this distance information is used to determine if aproper dosage has been delivered. If the actuator shaft has moved thedistance required to deliver the proper dosage, then in 1940, anindication that the proper dosage has been delivered is provided. If theactuator shaft has not moved the distance required to deliver the properdosage, then in 1950, the dosage delivered is calculated based on thedistance the actuator shaft has moved. In 1960, an indication of thedelivered dosage is provided.

FIG. 20 is a flow chart of one method relating to injecting a substanceinto an eye according to the principles of the present invention. FIG.20 relates to the situation in which the actuator shaft has stalled. In2010, the actuator is controlled based on a dosage and dosage rateinformation. The actuator moves the plunger to deliver the substance. In2020, data is received from a stall sensor. In 2030, this data is usedto determine if the actuator shaft has stalled. If the shaft hasstalled, then in 2040, an indication of the stall condition is provided.In 2050, data is received from a displacement sensor indicating thedistance that the actuator shaft moved. In 2060, an indication of thedelivered dosage is provided based on the distance information. If theshaft has not stalled, then in 2070, an indication is provided that theproper dosage has been delivered.

From the above, it may be appreciated that the present inventionprovides an improved system and methods for delivering precise volumesof a substance into an eye. The present invention provides a single use,disposable delivery device tip segment that is capable of delivering aprecise dosage. The tip segment interfaces with a limited reuseassembly. The present invention is illustrated herein by example, andvarious modifications may be made by a person of ordinary skill in theart.

While the present invention is described in the context of a single-usedrug delivery device, the present invention encompasses any single-usemedical device that interfaces with a source of electric power. Otherembodiments of the invention will be apparent to those skilled in theart from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. An ophthalmic injection system comprising: a tip segment attachableto and removable from a limited reuse assembly; the tip segmentcomprising: a dispensing chamber housing having an inner surface and anouter surface, the inner surface partially defining a dispensing chamberfor holding a quantity of a substance; a plunger engaged with the innersurface of the dispensing chamber housing, the plunger capable ofsliding in the dispensing chamber housing, the plunger fluidly sealed tothe inner surface of the dispensing chamber housing, the plunger havinga plunger interface; a needle fluidly coupled to the dispensing chamber;a temperature control device at least partially surrounding thedispensing chamber housing, the temperature control device for alteringa temperature of the substance in the dispensing chamber; and a firsthousing at least partially enclosing the dispensing chamber housing, thetemperature control device and the plunger the limited reuse assemblycomprising: an actuator having a shaft; a power source for providingpower to the actuator; a controller for controlling the actuator; amechanical linkage interface coupled to the shaft, the mechanicallinkage interface having a mating surface on an end, the mating surfacefor interfacing with the plunger interface; and a second housing atleast partially enclosing the power source, the controller, and theactuator; wherein the substance is injected after the temperature of thesubstance is altered.
 2. The system of claim 1 wherein the tip segmentfurther comprises: a thermal sensor located near the dispensing chamberhousing, the thermal sensor for measuring a temperature.
 3. The systemof claim 2 wherein the thermal sensor is selected from the groupconsisting of a thermocouple and a thermistor.
 4. The system of claim 2wherein the thermal sensor measures a temperature of the substance. 5.The system of claim 2 wherein a temperature of the substance isextrapolated from a temperature measured near the dispensing chamberhousing.
 6. The system of claim 2 further comprising: an interfaceconnecting the thermal sensor to the controller.
 7. The system of claim6 wherein the controller uses the temperature information to control thetemperature control device.
 8. The system of claim 6 wherein thecontroller uses the temperature information to control an injection ofthe substance.
 9. The system of claim 1 wherein the temperature controldevice is a heater.
 10. The system of claim 1 wherein the temperaturecontrol device is a cooling device.
 11. The system of claim 1 whereinthe temperature control device is a combination heating/cooling device.12. The system of claim 1 wherein the limited reuse assembly furthercomprises: a stall sensor for detecting if the actuator is experiencinga stall condition; and an interface for connecting the stall sensor tothe controller.
 13. The system of claim 1 wherein the limited reuseassembly further comprises: a displacement sensor for measuring adistance the actuator shaft travels; and an interface for connecting thedisplacement sensor to the controller.
 14. The system of claim 1 whereinthe power source is a battery.
 15. The system of claim 1 wherein theactuator is selected from the group consisting of a stepper motor, a DCmotor, a DC motor with a rotary sensor coupled to a linear drive, and aDC motor coupled to a linear drive with a linear sensor.
 16. The systemof claim 1 wherein the actuator is a spring driven mechanism.
 17. Thesystem of claim 1 wherein the actuator shaft is rigidly connected to themechanical linkage interface.
 18. The system of claim 1 wherein theactuator shaft is coupled to the mechanical linkage interface via a balland socket joint.
 19. The system of claim 1 wherein the tip segmentfurther comprises: a pair of tip interface connectors located on aninterfacing surface of the tip segment.
 20. The system of claim 19wherein the limited reuse assembly further comprises: a pair of limitedreuse assembly interface connectors located on an interfacing surface ofthe limited reuse assembly.
 21. The system of claim 20 wherein when thepair of tip interface connectors is coupled to the pair of limited reuseassembly interface connectors, the tip segment is electrically coupledto the limited reuse assembly.
 22. The system of claim 19 wherein thetip segment further comprises: a fuse electrically connected to the pairof tip interface connectors.
 23. The system of claim 22 wherein the fuseis blown thus preventing further use of the disposable injection device.24. The system of claim 19 wherein the temperature control device iselectrically coupled to the pair of tip interface connectors.
 25. Thesystem of claim 1 wherein the power source provides power to the tipsegment.
 26. The system of claim 1 wherein the power source providespower to the temperature control device.
 27. The system of claim 1wherein the tip segment further comprises: a memory device.
 28. Thesystem of claim 27 wherein the memory device is connected to a pair oftip interface connectors.
 29. The system of claim 27 in which thecontroller interfaces with the memory device.
 30. The system of claim 27wherein the memory device includes data about a condition of the tipsegment.
 31. The system of claim 30 wherein the controller uses the dataabout a condition of the tip segment to control an operation of the tipsegment.
 32. The system of claim 27 wherein the memory device includesdosage data.
 33. The system of claim 32 wherein the controller uses thedosage data to control an operation of the tip segment.
 34. The systemof claim 32 wherein the controller uses the dosage data to control anoperation of the actuator.
 35. The system of claim 32 wherein thecontroller uses the dosage data to control an operation of thetemperature control device.
 36. The system of claim 1 wherein thecontroller determines a distance to move the plunger to deliver a dosageof the substance.
 37. The system of claim 1 wherein the controlleroperates the actuator so that the actuator shaft moves at a fixed rate.38. The system of claim 1 wherein the controller operates the actuatorso that the actuator shaft moves at a variable rate.
 39. The system ofclaim 27 wherein the memory device is embodied in an RFID tag locatednear an interfacing surface of the disposable injection device.
 40. Thesystem of claim 39 wherein the limited reuse assembly further comprises:an RFID reader located near an interfacing end of the limited reuseassembly, the RFID reader adapted to read information from the RFID tag.41. The system of claim 1 wherein the plunger is press-fitted onto arigid shaft, and the plunger interface is located on a proximal end ofthe shaft.
 42. The system of claim 1 wherein the plunger is over-moldedonto a rigid shaft, and the plunger interface is located on a proximalend of the shaft.
 43. The system of claim 1 wherein the tip segmentfurther comprises: first and second tabs located on an interfacingsurface of the tip segment, the first and second tabs for securing thetip segment to the limited reuse assembly.
 44. The system of claim 43wherein the limited reuse assembly further comprises: first and secondslots located on an interfacing surface of the limited reuse assembly,the first and second slots for receiving the first and second tabs tosecure the tip segment to the limited reuse assembly.
 45. The system ofclaim 1 wherein the tip segment further comprises: a luer for securingthe needle to the dispensing chamber housing.
 46. The system of claim 1wherein the plunger interface has a shape that mates with a shape on anend of the mechanical linkage mechanism.
 47. The system of claim 1wherein motion is transferred from the mechanical linkage interface tothe plunger only in a single dispensing direction.
 48. The system ofclaim 1 wherein the substance is a drug for treating a condition of theeye.
 49. The system of claim 1 wherein the limited reuse assemblyfurther comprises: a power source controller for monitoring a conditionof the power source.
 50. The system of claim 1 wherein the limited reuseassembly further comprises: an indicator located on the housing, theindicator for providing information about a status of the limited reuseassembly.
 51. The assembly of claim 50 wherein the indicator is adisplay.
 52. The system of claim 1 wherein an initial amount of thesubstance is preloaded in the dispensing chamber and a dosage of thesubstance comprising less than the initial amount is delivered bymovement of the plunger in the dispensing chamber.
 53. An ophthalmicinjection system comprising: a tip segment attachable to and removablefrom a limited reuse assembly; the tip segment comprising: a dispensingchamber housing having an inner surface and an outer surface, the innersurface partially defining a dispensing chamber for holding a quantityof a substance; a plunger engaged with the inner surface of thedispensing chamber housing, the plunger capable of sliding in thedispensing chamber housing, the plunger fluidly sealed to the innersurface of the dispensing chamber housing, the plunger having a plungerinterface; a needle fluidly coupled to the dispensing chamber; atemperature control device at least partially surrounding the dispensingchamber housing, the temperature control device for altering atemperature of the substance in the dispensing chamber; a thermal sensorlocated near the dispensing chamber housing, the thermal sensor formeasuring a temperature near the dispensing chamber housing; a pair oftip interface connectors located on an interfacing surface of the tipsegment; and a first housing at least partially enclosing the dispensingchamber housing, the temperature control device and the plunger thelimited reuse assembly comprising: an actuator having a shaft; a powersource for providing power to the actuator; a controller for controllingthe actuator; a mechanical linkage interface coupled to the shaft, themechanical linkage interface having a mating surface on an end, themating surface for interfacing with the plunger interface; a pair oflimited reuse assembly interface connectors located on an interfacingsurface of the limited reuse assembly; a displacement sensor formeasuring a distance the actuator shaft travels; an interface forconnecting the displacement sensor to the controller; and a secondhousing at least partially enclosing the power source, the controller,and the actuator; wherein the substance is injected after thetemperature of the substance is altered.
 54. The system of claim 53further comprising: an interface connecting the thermal sensor to thecontroller.
 55. The system of claim 54 wherein the controller uses thetemperature information to control the temperature control device. 56.The system of claim 54 wherein the controller uses the temperatureinformation to control an injection of the substance.
 57. The system ofclaim 53 wherein the thermal sensor is selected from the groupconsisting of a thermocouple and a thermistor.
 58. The system of claim53 wherein the temperature control device is a heater.
 59. The system ofclaim 53 wherein the temperature control device is a cooling device. 60.The system of claim 53 wherein the temperature control device is acombination heating and cooling device.
 61. The system of claim 53wherein the limited reuse assembly further comprises: a stall sensor fordetecting if the actuator is experiencing a stall condition; and aninterface for connecting the stall sensor to the controller.
 62. Thesystem of claim 53 wherein the power source is a battery.
 63. The systemof claim 53 wherein the actuator is selected from the group consistingof a stepper motor, a DC motor, a DC motor with a rotary sensor coupledto a linear drive, and a DC motor coupled to a linear drive with alinear sensor.
 64. The system of claim 53 wherein the actuator is springdriven mechanism.
 65. The system of claim 53 wherein the actuator shaftis rigidly connected to the mechanical linkage interface.
 66. The systemof claim 53 wherein the actuator shaft is coupled to the mechanicallinkage interface via a ball and socket joint.
 67. The system of claim53 wherein when the pair of tip interface connectors is coupled to thepair of limited reuse assembly interface connectors, the tip segment iselectrically coupled to the limited reuse assembly.
 68. The system ofclaim 53 wherein the tip segment further comprises: a fuse electricallyconnected to the pair of tip interface connectors.
 69. The system ofclaim 68 wherein the fuse is blown thus preventing further use of thedisposable injection device.
 70. The system of claim 53 wherein the tipsegment further comprises: a memory device.
 71. The system of claim 70wherein the memory device is connected to the pair of tip interfaceconnectors.
 73. The system of claim 71 wherein the controller interfaceswith the memory device.
 73. The system of claim 70 wherein the memorydevice includes data about a condition of the tip segment.
 74. Thesystem of claim 73 wherein the controller uses the data about acondition of the tip segment to control an operation of the tip segment.75. The system of claim 72 wherein the memory device includes dosagedata.
 76. The system of claim 75 wherein the controller uses the dosagedata to control an operation of the tip segment.
 77. The system of claim75 wherein the controller uses the dosage data to control an operationof the actuator.
 78. The system of claim 75 wherein the controller usesthe dosage data to control an operation of the temperature controldevice.
 79. The system of claim 53 wherein the controller determines adistance to move the plunger to deliver a dosage of a substance.
 80. Thesystem of claim 53 wherein the controller operates the actuator so thatthe actuator shaft moves at a fixed rate.
 81. The system of claim 53wherein the controller operates the actuator so that the actuator shaftmoves at a variable rate.
 82. The system of claim 70 wherein the memorydevice is embodied in an RFID tag located near an interfacing surface ofthe disposable injection device.
 83. The system of claim 82 wherein thelimited reuse assembly further comprises: an RFID reader located near aninterfacing end of the limited reuse assembly, the RFID reader adaptedto read information from the RFID tag.
 84. The system of claim 53wherein motion is transferred from the mechanical linkage interface tothe plunger only in a single dispensing direction.
 85. The system ofclaim 53 wherein the substance is a drug for treating a condition of theeye.
 86. The system of claim 53 wherein an initial amount of thesubstance is preloaded in the dispensing chamber and a dosage of thesubstance comprising less than the initial amount is delivered bymovement of the plunger in the dispensing chamber.